1. Field of the Invention
The present invention relates to a multilayer capacitor and a manufacturing method for a multilayer capacitor. More particularly, the present invention relates to an ultra-small multilayer capacitor and a manufacturing method for an ultra-small multilayer capacitor.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2007-299984 discloses a multilayer capacitor that is intended to reduce variations of an electrostatic capacitance. Generally, a multilayer capacitor is designed to have the desired electrostatic capacitance. Parameters determining the electrostatic capacitance of the multilayer capacitor include the dielectric constant of a dielectric that constitutes ceramic layers, i.e., effective dielectric layers, the area of a region where a pair of electrodes is opposed to each other with the ceramic layers sandwiched therebetween, the distance between the electrodes, and the number of the laminated ceramic layers. The electrostatic capacitance of the multilayer capacitor is proportional to the dielectric constant of the dielectric, the area of the region where the pair of electrodes is opposed to each other, and the number of the laminated ceramic layers, whereas it is reversely proportional to the distance between the electrodes. In designing the multilayer capacitor having the desired electrostatic capacitance, it has so far been usual to employ one of the following three adjustment methods.
In a first adjustment method, the number of the laminated ceramic layers is increased or decreased. In a second adjustment method, the distance between the electrodes is increased or decreased by changing the thickness of the ceramic layer. In a third adjustment method, the area of the region where the pair of electrodes is opposed to each other is increased or decreased by shifting the arranged positions of the pair of electrodes.
In the case of a multilayer capacitor downsized to an ultra-small size, the number of the laminated ceramic layers is reduced. Therefore, a change rate of the electrostatic capacitance caused by increasing or decreasing the number of the laminated ceramic layers is increased relatively. In more detail, when the number of the laminated ceramic layers is 200, the electrostatic capacitance per ceramic layer occupies just 0.5% of that of the entire multilayer capacitor, and the electrostatic capacitance can be adjusted in units of 0.5%. However, when the number of the laminated ceramic layers is 50, the electrostatic capacitance per ceramic layer occupies 2% of that of the entire multilayer capacitor, and when the number of the laminated ceramic layers is 10, the electrostatic capacitance per ceramic layer occupies 10% of that of the entire multilayer capacitor.
Thus, as the number of the laminated ceramic layers is reduced, the electrostatic capacitance of the multilayer capacitor is changed to a larger extent depending on an increase or a decrease in the number of the laminated ceramic layers. It is therefore difficult, in the ultra-small multilayer capacitor, to obtain the desired electrostatic capacitance by the adjustment method of increasing or decreasing the number of the laminated ceramic layers.
When a proportion of the electrostatic capacitance per ceramic layer with respect to that of the entire multilayer capacitor is large, the electrostatic capacitance of the multilayer capacitor is greatly changed depending on an increase or a decrease in the distance between the electrodes. In the ultra-small multilayer capacitor, therefore, it is also difficult to obtain the desired electrostatic capacitance by the adjustment method of increasing or decreasing the distance between the electrodes.
Moreover, in the multilayer capacitor downsized to the ultra-small size, a space usable to shift the positions of the pair of electrodes relative to each other is reduced from the viewpoint of ensuring moisture resistance, etc., and a difficulty occurs in shifting the positions of the pair of electrodes to increase or decrease the area of the region where the pair of electrodes is opposed to each other. Accordingly, it is difficult, in the ultra-small multilayer capacitor, to obtain the desired electrostatic capacitance by the adjustment method of shifting the positions of the pair of electrodes, thereby increasing or decreasing the area of the region where the pair of electrodes is opposed to each other.
Thus, the ultra-small multilayer capacitor has a difficulty in obtaining the desired electrostatic capacitance by the ordinary adjustment methods.